1. Field of the Invention
The invention relates to a device for localizing secondary surveillance radar (SSR) transponders, as specified in Annex 10 to the Convention of Chicago 1944 of ICAO, at an airport.
2. Description of the Prior Art
Devices of the type specified above comprise plurality of transmitters for transmitting an interrogation signal, and a plurality of receivers for receiving the response signal of an SSR transponder. The airport is divided in a plurality of divisional regions, and the transmitters are suitable to transmit interrogating signals to make an SSR transponder present in a predetermined divisional region respond. The device also includes means for controlling said transmitters such that the transmitter or transmitters interrogating different divisional regions transmit successively pulses, which in the different divisional regions are received as interrogating signals P1, P3. These interrogating signals comprise a first pulse P1, possibly after a first predetermined period, a second pulse P2 of smaller reception strength than the first pulse, and at a second predetermined period after the time allotted to the second pulse a third pulse P3. The SSR transponders are muted during a time longer than the sum of said first and second periods after reception of a second pulse of greater or equal strength to the first pulse.
An example of such a device is known from the U.S. Pat. No. 5,179,384 to De Haan.